Chadwick-Helmuth 8500C User Manual

2-8
Chadwick-Helmuth Company, Inc.
Chapter 2
- Overview and Basic Theory
Each balance chart contains data that describe a single rotor element from a particular aircraft type. In
the 8500C/C+, related balance charts are stored digitally in a balance chart file. They may also b
represented graphically and can be found in almost any Chadwick-Helmuth paper balance chart. Paper
balance charts provide a simple way to visually fix a balance measurement and calculate the weight
adjustments required to balance the rotor. Although the 8500C/C+ does not require the use of paper
balance charts, it does use the information they contain. It is therefore important for purposes of ou
discussion to understand some of the theory behind them.
2.2.2.1 Paper Balance Charts
A paper balance chart consists of a clock face who se 12radial lines represent the clock angle of th
balance measurement (see Figur e2-6). Concentric circles drawn around the center of the clock face
delimit different values of vibration amplitude. Finally, a graph is laid over the clock face. The graph’s
axes represent the geometrical relationship between the weight attachment points of the aircraft. If, for
example, the attachment points are 9 0 °apart, as on a four-blade rotor, the axes of the graph are
perpendicular to each other. The axes are labeled with weight amounts, and their values are inversely
proportional to the length of the moment arm formed by the center of rotation and the weight
attachment point (a weight has more effect the further out it is placed along a blade, so smaller
amounts are needed).
Figure 2-6. Sample Paper Balance Chart
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Chadwick-Helmuth 8500C Specifications

General

Brand	Chadwick-Helmuth
Model	8500C
Category	Measuring Instruments
Language	English